Complex anionic metal sulfides and process for their preparation

ABSTRACT

Transition metal complex sulfides containing the NH 2  R 2   +  group are prepared by treating the hydrogen sulfide an organic solution of a carbomate having the general formula: 
     
         Me.sup.z (O.sub.2 CNR.sub.2).sub.z 
    
     in which Me is a transition metal and R an alkyl group.

FIELD OF THE INVENTION

The present invention refers to complex metal sulfides employable assemi-conductors or as materials having photoelectric activity, and to aprocess for their preparation.

PRIOR ART

In recent years various investigations were made with the purpose offinding metal sulfides having photoelectric properties and processes fortheir preparation.

For example, the polycrystalline FeS₂ was prepared and characterized (A.Ennaoni, S. Fiechter et al "Photoactive synthetic polycrystallinepyrite" Electrochemical Science and Technology, 1579-82. July 1985).

A vast class of transition metal chalcogenides was also investigated (M.Tributsch, "Photoelectrochemical energy conversion involving transitionmetal d-states", Structure and Bonding 49, 127-175 1982).

More recently the use of alkoxides as intermediates for the formation ofsulfides (H. P. Boehm, E. Flaig, Angew.Chem 78, 987, 1966) and of oxides(M. L. H. Chisholm, I. P. Rothwell, Alkoxides and Aryloxides, in G.Wilkinson, R. D. Gillard, J. A. McCleverty, Eds., ComprehensiveCoordination Chemistry, Pergamon Press, Oxford, Vol. 2, 1987, pp.335-364) has been thoroughly investigated.

SUMMARY OF THE INVENTION

We have found new complex anionic metal sulfides of general formula (i)

    (NH.sub.2 R.sub.2).sub.m Me.sup.z.sub.p S.sub.q            (I)

in which m, q and p are bound by the following relationship:

    m=2q-zp

    R=C.sub.2 -C.sub.5 alkyl

    Me=transition metal

    z=oxidation state

Said sulfides are prepared by dissolving in a anhydrous organic solventa carbamate of general formula (II)

    Me.sup.z (O.sub.2 CNR.sub.2).sub.z                         (II)

followed by a treatment with hydrogen sulfide, filtration of theprecipitate, washing with an organic solvent and drying.

DETAILED DESCRIPTION OF THE INVENTION

The characteristics and the advantages of the complex anionic metalsulfides of general formula (I) and of the process for their preparationwill be further evidenced by the following detailed description.

The sulfides according to the present invention belong to transitionmetals, particularly, Fe, Co, Ni, Cu and other of series 3d, in theirusual and less usual oxidation states.

The alkyl groups bound to the nitrogen atom, which may be equal ordifferent, are the ones having 2 to 5 carbon atoms, in particular,ethyl, isopropyl, n- or isobutyl, amyl.

For the preparation of the complex metal sulfides of general formula(I), the corresponding complex N,N-dialkylcarbamates of general formula(II) are dissolved in anhydrous organic solvents inert vis-a-vis thecompounds in question.

Preferred solvents are aliphatic and aromatic hydrocarbons, particularlypreferred are n-heptane and toluene. Mixtures of two or morehydrocarbons may also be employed.

The solution has a N,N-dialkylcarbamate concentration of between 1 and10-2 moles/l. In certain cases one can avoid dissolving the preparedmetal carbamate employing as starting materials the solutions obtainedby treating the corresponding anhydrous metal halide with the secondaryamine and CO₂, in a hydrocarbon solvent, after elimination of NH₂ R₂ Xand by partially evaporating the excess amine used in the reaction forproducing the carbamate.

The carbamate containing solution is treated with hydrogen sulfide at0°-30° C. for 1 to 24 hrs.

The precipitate is filtered off, washed with a solvent of the typeemployed in the preparation and dried at room temperature under reducedpressure.

The yield is practically quantitative and the product shows high purity.It is sensitive to oxygen, and, in air, develops SO₂ and H₂ S; bytreatment with a concentrated hydrochloric acid solution in a inertatmosphere only H₂ S is evolved.

The obtained sulfides (I) show electrical characteristies suitable totheir use as semiconductors and as materials having photoelectricactivity.

The process according to the invention presents the followingadvantageous characteristics:

(a) as the dialkylcarbamate (O₂ CNR₂) group contains the elements ofcarbon dioxides, it is an excellent exiting group.

(b) The presence of the NR₂ residual leads almost necessarily to theformation of anionic sulfides.

Finally, there is the possibility of exchanging the NH₂ R₂ ⁺ group withother cations, so as to obtain bimetallic sulfides.

As illustrative examples of the chemical reaction leading to theformation of the sulfides (I) according to the present invention, thefollowing may be reported:

    6Co(O.sub.2 CNEt.sub.2).sub.2 +7H.sub.2 S→(NH.sub.2 Et.sub.2).sub.2 CO.sub.6 S.sub.7 +12Co.sub.2 +10NHEt.sub.2

    8Ni(O.sub.2 CNEt.sub.2).sub.2 +9H.sub.2 S→(NH.sub.2 Et.sub.2)Ni.sub.8 S.sub.9 +16CO.sub.2 +14NHEt.sub.2

    8Fe(O.sub.2 CNEt.sub.2).sub.3 +15H.sub.2 S→(NH.sub.2 Et.sub.2).sub.6 Fe.sub.8 S.sub.15 +24CO.sub.2 +18NHEt.sub.2

    16Fe(O.sub.2 CNiPr.sub.2).sub.3 +29H.sub.2 S→(NH.sub.2 iPr.sub.2).sub.10 Fe.sub.16 S.sub.29 +48CO.sub.2 +38NHiPr.sub.2

The following examples of the preparation of sulfides (I) are reportedto illustrate the present invention, without limiting it.

EXAMPLE 1

0.497 g (1,71.10⁻³ moles) Co(O₂ CNEtPv2Pv)₂ and 10 ml toluene. wereintroduced in a 100 ml distillation flask in a nitrogen atmosphere.After saturation with gaseous H₂ S, the mixture was left under stirringat room temperature for one day. The black solid obtained was filteredoff, washed with toluene and dried at room temperature with the aid of amechanical pump (10⁻² torr) for 4 hrs. 0.152 g (73.4%) of a product wasobtained which the analysis showed to correspond to (NH₂ Et₂)₂ Co₆ S₇.Elemental analysis: found % (calculated for C₈ H₂₄ N₂ Co₆ S₇) C:11,6(13,2); H:3,0 (3,3); N:3,0 (3,8); Co:48,6 (48,7), S:29,2 (30,9).

Resistivity=490,88 10⁻³ /Ω cm

EXAMPLE 2

4.65 g (0.016 moles) Ni(O₂ CNEt₂)₂ and 100 ml n-eptane were introducedin a 250 ml distillation flask in a nitrogen atmosphere.

After saturation with gaseous H₂ S, the mixture was left under stirringat room temperature for 1 day. The black solid obtained was filteredoff, washed with n-heptane and dried with the aid of a mechanical pump10⁻² torr) at room temperature for 10 hrs. 1.69 g (93%) of a solid wereobtained which the analysis showed to correspond to (NH₂ Et₂)₂ Ni₈ S₉.

Elemental analysis: found % (calculated for C₈ H₂₄ N₂ Ni₈ S₉) C:10.4(10.6); H:2.6 (2.7); N:2.9 (3.1); Ni:50.5 (51.8); S:32.9 (31.8).

Resistivity=350.624 10⁻³ /Ω cm

EXAMPLE 3

16.81 g (3.4 10⁻² moles) [Fe(O₂ CN iso-Pr₂)₃ ]_(n) and 160 ml of a 1/1toluene-n-heptane mixture were introduced in a 200 ml distillation flaskin a nitrogen atmosphere. After saturation with gaseous H₂ S, themixture was left under stirring at room temperature for one day. Theblack solid obtained was filtered off, washed with a 1/1toluene-n-heptane mixture and dried at room temperature for 4 hrs withthe aid of a mechanical pump (10⁻² torr). 5.22 g (85%) of a productcorresponding at the analysis to the formula (NH₂ iso-Pr₂)₁₀ Fe₁₆ S₂₉wee obtained. Elemental analysis: % found (calculated for C₆₀ H₁₆₀ Fe₁₆N₁₀ S₂₉):C,25.2(25.3);H,5.3);(5.7);Fe,31.7(31.4);N,4.2(4.9);S;31.5(32.7).

EXAMPLE 4

9.66 g (2.39 10⁻² moles) of [Fe(O₂ CNEt₂)₃ ]_(n) and 100 ml toluene wereintroduced in a 250 ml distillation flask in a nitrogen atmosphere.After saturation with gaseous H₂ S, the mixture was left under stirringat room temperature for 1 day. The black solid obtained was filteredoff, washed with toluene and dried with the aid of a mechanical group(10⁻² torr) at room temperature for 4 hrs. 3.98 g (97%) of a productcorresponding by analysis to (NH₂ Et₂)₆ Fe₈ S₁₅ were obtained.

Elemental analysis: % found (calculated for C₂₄ H₇₂ Fe₈ N₆ S₁₅);C,21.0(21.0); H, 5.2(5.3); Fe, 30.4(32.5); N,6.0(6.1); S, 35.8(35.0).

Resistivity=157.08 10⁴ Ω cm

EXAMPLE 5

Anhydrous cupric chloride (3.79 g, 29.2 mole) prepared from the hydratedform by treatment with thionyl chloride, was suspended in anhydroustoluene (100 ml) in a nitrogen atmosphere. After evacuating the system,carbon dioxide at normal pressure and 19.88 g diethylamine (272 moles)were added and the mixture was stirred for 5 hrs at room temperature.

The colorless precipitate consisting of diethylammonium chloridrate wasfiltered off and the blue colored solution was concentrated underreduced pressure and at room temperature to about half of its initialvolume.

The resulting solution, containing copper (II) N,N-diethylcarbamate,Cu(O₂ CNEt₂)₂, was treated with H₂ S previously dried through calciumchloride absorption tower. Immediate precipitation of a black solid wasobserved. The H₂ S treatment was repeated several times to make surethat the reaction was completed. The complex cupric sulfide obtained wasfiltered off, repeatedly washed with toluene and dried with for 14 hrsat room temperature with the aid of a mechanical pump (2.09 g; 66% yieldon the basis of the copper content of this product). The results of theanalysis correspond to a composition [NH₂ (C₂ H₅)₂ ]₂ [Cu₁₄ S₁₅ ].

Elemental analysis: found % (calculated for C₈ H₂₄ Cu₁₄ N₂ S₁₅); C,6.0(6.3); H, (1.6); Cu, 56.3(58.6); N, 1.6(1.8).

Resistivity=147,26 10⁻³ Ω cm.

EXAMPLE 6

Example 5 was repeated for preparing a solution of copper (II)N,N-di-isopropylcarbamate, Cu (O₂ CNiPr₂)₂, which was then treated withH₂ S as in Example 5, to obtain the corresponding isopropyl cupricsulfide.

Resistivity=490.88 10⁻³ /Ω cm.

We claim:
 1. Complex anionic metal sulfides having the general formula(I):

    (NH.sub.2 R.sub.2).sub.m Me.sup.z.sub.p S.sub.q            (I)

ion which m, q and p are bound by the following relation: m=2q-zp R=C₂-C₅ alkyl Me=transition metal z=oxidation state
 2. Sulfides according toclaim 1, wherein said transition metal may be Fe, Co, Ni, Cu or anothermetal of the 3d series in their usual and less usual oxidation states.3. Sulfides according to claim 1, wherein said alkyl is: ethyl,isopropyl, butyl, amyl.
 4. Process for the preparation of complexanionic metal sulfides of general formula (I)

    (NH.sub.2 R.sub.2).sub.m Me.sup.z.sub.p S.sub.q            (I)

in which m, p and q are bound by the following relation: m=2q-zp R=C₂-C₅ alkyl Me=transition metal z=oxidation state wherein a solutioncontaining the corresponding carbamates of general formula (II)

    Me.sup.z (O.sub.2 CNR.sub.2).sub.z                         (II)

in inert, anhydrous organic solvents, is treated with hydrogen sulfideand the precipitate in filtered off, washed and dried.
 5. Processaccording to claim 4, wherein the solution, treated with hydrogensulfide, is the solution obtained by treating the anhydrous metal halidewith a secondary amine and CO₂ in a hydrocarbon solvent, after the NH₂R₂ X has been eliminated from said solution, and after partialevaporation to eliminate the excess of the amine employed in thereaction for obtaining the carbamate.
 6. Process according to claim 4,wherein said organic solvents are aliphatic and aromatic hydrocarbons.7. Process according to claim 4, wherein said solvents are n-heptane,toluene or their mixtures.
 8. Process according to claim 4, wherein theorganic solvent solution has a concentration of said carbamate ofbetween 1 and 10⁻² moles/l.
 9. Process according to claim 4, whereinsaid hydrogen sulfide treatment is performed at a temperature between 0°and 30° C.
 10. Process according to claim 4, wherein said hydrogensulfide treatment is continued for 1 to 24 hours.
 11. Process accordingto claim 4, wherein said drying of the product is performed underreduced pressure at room temperature.
 12. Complex anionic metal sulfideshaving the formula

    (NH.sub.2 R.sub.2).sub.m Ni.sup.z.sub.p S.sub.q

in which m, q, and p are bound by the following relation: m=2q-zp, R=C₂-C₅ alkyl, and z=oxidation state.